“2019 is really turning out to be not just an active year, but a very active year,” said state epidemiologist Dr. Catherine Brown.

Dr. Brown said several factors are contributing including changing temperatures and precipitation along with the shifting types of mosquito species.

“Because we’re seeing an increase in the populations of the mammal biting mosquitoes, we think that might be one of the reasons that the cycle is changing a little bit as well,” Dr. Brown said.

Earlier this week, DPH and the Department of Agricultural Resources said aerial spraying in specific areas of Worcester and Middlesex counties is scheduled to begin Sunday, Aug. 25. As a result of the elevated risk in several communities, the spray zone has been expanded. The additional communities either partially or fully in the spray zone are Blackstone, Douglas, Dudley, Holliston, Hopedale, Mendon, Millville, Oxford, Uxbridge and Webster.

In total across Massachusetts, there are 23 communities now at critical risk, 22 at high risk and 52 at moderate risk for the EEE virus. So far, EEE has been found in 330 mosquito samples this year, many of them from species that can spread the virus to humans.

EEE symptoms can range from a stiff neck, headache and lack of energy to dangerous complications like inflammation and swelling of the brain.